The elucidation of how lysozyme exerts its muramidase, "lectin-like", cationic and hydrophobic effects to fulfil its biological role in host defense is the main objective of our research. Through an in-depth in vitro investigation of lysozyme's bacteriolytic, bactericidal and bacterial aggregating properties, a better understanding of lysozyme's in vivo antibacterial role should emerge. Since the microbicidal activity of lysozyme may be dependent upon mechanisms similar to those reported for leukocyte cationic proteins, this proposal will examine the virtually unexplored antibacterial effects of parotid salivary cationic proteins. Cationic proteins and other salivary components will be tested in conjunction with lysozyme for potential synergistic antibacterial effects. An understanding of how lysozyme may function in the immune response will be achieved through studies of the interaction of lysozyme with human mononuclear cells. Screening techniques for the identification of lysozyme receptors will be developed and receptors on bacterial and mammalian cells will be isolated and characterized. The molecular nature of the interaction of the purified receptors with lysozyme will also be investigated. Such studies will be of particular significance since several of these bacterial receptors have been implicated in the pathogenesis of dental caries and periodontal disease. Using similar screening procedures, the lysozyme binding components of parotid saliva will be isolated and characterized. A radioimmunoassay for parotid lysozyme will be developed for quantitation of true concentrations of lysozyme in freshly isolated and fractionated human parotid saliva.